1. Field of the Invention
This invention relates to a power supply circuit configuration providing improved voltage regulation for a CRT, and, more particularly, to a regulated power supply circuit configuration which provides a voltage feedback loop between the portion of a CRT power supply providing operating potential to the screen electrode and the portion of the power supply providing operating potential to the anode of the CRT.
2. Description of the Prior Art
Video display systems are well-known devices and have been used for many years as a readout device in conjunction with computer terminal equipment or other such systems where it is desirable to have a visual presentation of text or sensor information. The actual display device is often a CRT having a phosphorous coating on the faceplate across which an electron beam is swept in vertically adjacent lines to form a composite image. The electron beam is generated by a gun situated in the neck portion of the CRT, and it is modulated by an electrical signal applied to a control element which varies the beam intensity and, in turn, the light output of the phosphor coating. Proper operation of the CRT requires that the power supply providing DC operating potentials to the anode not deviate significantly. If coupled to the deflection circuitry, this potential is normally regulated so that during periods of high beam current, the load on the power supply will not pull down the effective DC voltage.
Some prior art devices for providing a relatively constant DC operating potential to the anode have involved an independent power supply which is completely separate from the horizontal deflection circuitry for the CRT. While it is possible to achieve a high degree of regulation by separating the power supply function and the horizontal deflection function, these devices are inherently costly since many component parts are required in the respective units.
Other devices for regulating DC operating potential supplied to the anode have involved the regulation of a lower voltage power supply, such as the primary side of a transformer, and just presume that the high voltage will be maintained essentially constant. Because the actuatable operating potential supplied to the anode is not sensed, these devices are inherently less accurate than a direct sensing device.